Hello Kate, I think I may be able to give some more information.
Arthur (born 1906) was may garndfathers brother. My garndfather waa Frederick Charles Prinsep, who was married to Rosemary Prinsep (nee Brockington). They also had a brother and sister, Louis Prinsep and Nelly Prinsep, (Nelly married Albert Poole).
If I start with my grandfather, Fred, he had two sons, Louis Arthur (my father) and Roy, and one daughter, Peggy.
Louis Prinsep (Arthurs other brother) was married to Mildred. They had three children, Michael, Roger and Peter.
Nelly Prinsep had four children, Albert, Jean, Rosemary and John.
My father married Beryl Penson (my mother),and I have a sister Lucy from my fathers second marriage.
I am 44 years old and married to Gillian Martin and we have have two sons, Lee who has just turned 17, and Lucas who is 11.
My aunt (Peggy)who married Terry Roberts had one daughter named Kim who is now 41 years old.
My uncle (Roy) had five children, Roy junior, Thomas, Gerrard, Susan and Gary. I am not sure of thier ages but they must range from around 30 to 40.
Thats about as much information as my dad and I can come up with, but hopefully it will throw a little more light on the Prinsep family.
Unfortunately my grandfather (Fred) and grandmother (Rose) have both passed away. I am sure that they could have givenmuch more information.
I will contact my aunt Peggy and ask her if she has any more information, and if so will forward this to you.
Please contact me at david- firstname.lastname@example.org to exchange comments.